There is already well-known a process of metallizing employing thin metal sheets and especially applied to variously sectioned ledges to obtain gilded frames and the like.
With special reference to the constant-sectioned wooden ledges, which are those mostly produced, the known process of metallizing (as for instance the gilding or silver plating with thin metal sheets) comprises the following steps, which are performed after the ledge of an adequate shape has been obtained in a conventional way by means of traditional machinery;
1 -- THE SURFACE TO BE TREATED IS COVERED WITH SPECIAL PRODUCTS, SUCH AS CHALK AND OTHER MORE REFINED PRODUCTS, TO OBTAIN A SMOOTH AND STABILIZED SURFACE IN AN ECONOMICAL AND RAPID MANNER
2 -- THE SEMI-FINISHED PRODUCTS SO OBTAINED ARE COVERED WITH A FURTHER SURFACE COVERING ACTING AS AN ADHESIVE FIT FOR RECEIVING THE THIN METAL SHEETS;
3 -- THE LEDGE SURFACE TO BE TREATED IS MANUALLY COVERED WITH THIN METAL SHEETS MADE OF GOLD, PINCHBECK, SILVER OR THE LIKE, BRONZE OR THE LIKE, COPPER OR THE LIKE, ETC., IN ORDER TO OBTAIN THE DESIRED METALLIC APPEARANCE;
4 -- THE FIXING OPERATION OF THE APPLIED THIN METAL SHEETS IS THEN MANUALLY PERFORMED.
With special reference to the operations mentioned in (3) and (4), it is well-known that the ledge surface covering is carried out using small metal sheets whose dimensions do not exceed the 20 .times. 20 cm. size and their thickness is extremely reduced. They are manually made to adhere to the surface to be covered and they are laid one after the other, slightly overlapping. When such an operation is over, a piece of cotton-wool is then manually passed on the covered surface to make these sheets adhere thoroughly on the surface of the ledge and/or the structural shape. The operation will be effected paying attention to pass on the surface and to "smooth" it always following the only direction made possible by the scale overlapping in order to avoid the lifting up and breaking of the sheet edges before they adhere thoroughly to the surface.
As is easily understood, such a procedure implies not only a long and burdensome work, but also a remarkable quantity of labor. What is more, the percentage of wasted metal sheet material is high due to the fact that the sheet metal supplied has standard dimensions and so a good deal of this expensive material (30 to 50 percent) is to be cut off especially from the transversely exceeding sides of the small sheets. Such a waste becomes more and more noticeable when structural shapes having a small transverse development have to be covered. Besides, a supplying of metal sheets having a reduced breadth would not solve the problem because it would not be suitable to all the possible different developments of the metal sheets and it would not be handy. Even if such a drawback could be avoided, the remarkable quantity of labor required would still weigh heavily on the effectiveness of this process.
Therefore, when treating flat surfaces, such metal sheets have been replaced by metal sheet tapes supported by a pull-resistant tape. Such tapes are lengthwise and not transversely applied to the surface.
The use of the tape is remarkably advantageous because it allows diminishing the quantity of labor. But up to today it is still used only for flat surfaces because the problem of covering complex structural shapes - particularly those having concave parts - has not been solved yet.
As a matter of fact, the tape would not fit well on such structural shapes, especially on the concave parts, because the metal sheet rolled on a tape adheres immediately on the surface to be covered as soon as it is laid on the surface and in this way the metal sheet cannot conform adequately to the curvings of the structural shape. In fact, when considering the convex curvings, such a drawback is avoided making the tape, which is forced to adhere along one only longitudinal line, adhere progressively on one side and on the other of such longitudinal line. But acting in this way is not possible when the curvings of the surface to be treated are concave because the tape would adhere on two longitudinal lines on one side and on the other of the concave part, so that, when pressing the tape against the surface, a central longitudinal crack spreading all around would occur and the metallizing itself would be ruined.